The present invention consists of a tooth preparation instrument and system that creates a tapered conical shape from a tooth, with pre-determined dimensions, making it possible for a lab technician to independently and simultaneously create a crown that exactly fits the prepared tooth. The crown is ready for permanent placement on the prepared tooth at the time of preparing the tooth. Use of the invention saves considerable time and effort as compared with current methods.
Currently, a tooth is prepared for a crown in the following manner. First, during an initial office visit, the dentist makes an impression of the portion of the mouth in which the tooth is located, with upper and lower occusal surfaces. From this impression a lab technician will later create a stone study model.
The dentist then removes tooth material with a high-speed drill, relying on eyesight and expertise to create a form on which a crown will be cemented. This form begins with a narrow shoulder at the gum line and tapers inward as it rises to a flattened top that ends just below the lowest level of the tooth""s original biting surface.
The dentist then makes an impression of the prepared tooth and sends it to the lab technician along with the tooth impression, prepared prior to removal of tooth material. The dentist makes and installs a temporary crown for the prepared tooth.
Using the impression of the prepared tooth, the lab technician produces a crown that matches the dentist""s color and material specifications and sends it to the dentist. At the patient""s second visit, the dentist tests and adjusts the crown as necessary before cementing it in place.
By the present invention, the following steps will be performed. At an initial office visit, the dentist makes an impression of the portion of the mouth in which the tooth is located, with upper and lower occusal surfaces. From this impression the lab technician will later create a stone study model.
The dentist, at a second office visit or, in a preferred embodiment, during the same office visit when a lab technician is available in the office for simultaneous creation of the crown, presses a surface contour tool against the biting surface of the tooth to determine the depth settings for at least one burr in a surface tool that will remove the upper surface of the tooth and create a working surface for the material removal device.
The dentist inserts at least one burr with the proper length in this tool so that when the tool is lowered onto the tooth, a flat surface will be created. It is essential that this surface be aligned perpendicular to the center line of the tooth. The dentist also calculates the center of the tooth and sets the depth of the burr that will drill the center hole for guiding the material removal device.
The flat surface tool and the center hole drilling burr are operated with a device that locks onto the tooth and ensures that the top surface of the tooth will be perpendicular to the central line of the tooth. The dentist makes two calculations. First, the distance in 0.1 mm increments between a predetermined point below the lowest level on the tooth""s biting surface (beginning level) and the gum line (ending level). This will be the height of the prepared tooth. The second calculation is the distance from the center of the tooth""s biting surface to a predetermined point inside the narrowest part of the tooth at the gum line (the shoulder). This will be the radius at the shoulder of the prepared tooth. The dentist inserts tapered burrs of predetermined lengths and a guide pin of the required length into the material removal device and feeds the calculations into a computer processor which will control the material removal device. A print out of the calculations is forwarded to the technician for confirmation of the requirements for the prepared crown or a bridge.
To initiate operation of the material removal device, a center hole is drilled. A flat surface tool is used to remove tooth material, smoothing the surface as necessary. The dentist inserts the guide pin of the material removal device in the center hole and begins to remove material from the side of the tooth. Each cycle around the tooth removes 0.1-0.5 mm. The various burrs are tapered and may be diamond burrs to create the required chamfer on the sides of the tooth.
The device has four computer controlled lights to guide the dentist. A green light indicates that the device is level with the top surface. A blue light is activated when a desired depth is achieved as also limited by the length of the burr. Two lights (one red and one yellow) warn the dentist that the device is tilted so that it is creating an undercut (red) or drilling too far toward the outer edge of the shoulder (yellow).
After each cycle, the dentist moves the depth setting another 0.1-0.5 mm until the required depth is reached. The burrs on the device, ranging in number from one to six, are preset so that they cannot be extended beyond the depth that has been calculated by the dentist.
While the dentist has been removing tooth material the lab technician has independently and simultaneously, if the technician is immediately available produced a crown or bridge that will fit the prepared tooth. The prepared crown will have the same internal dimensions as the prepared tooth and also the same characteristics (color, shape) as the original tooth.
Some of the advantages of the invention are that a dentist can prepare a tooth knowing that the crown will fit precisely, because the prepared tooth will have the same exterior dimensions as the interior opening on the crown so that the crown will precisely fit the prepared tooth. In addition, only one office visit is necessary to prepare the tooth and install a permanent crown. A patient will not require a temporary crown. The dentist will not have to make an impression of the prepared tooth and wait for the technician to produce the crown.
Alternatively, a series of pre-prepared crowns of various shapes and colors may be available to the dentist. Since the tooth will be prepared to a predetermined truncated cone size, pre-formed crowns having a similar pre-formed internal truncated conical recess may be available to the dentist. This would insure immediate accurate crown installation during a single office visit.
Accordingly, it is an object of the present invention to provide a tooth preparation instrument and system of its use including preparing an impression of a portion of a mouth in which a diseased tooth is located and simultaneously preparing or using a pre-formed permanent crown during the same office visit during which the impression was made with the crown having a predetermined internal recess calculated to exactly match a predetermined prepared tooth size so that the crown may be permanently secured to the prepared tooth during a single office visit.
It is another object of the present invention to prepare a tooth based upon a predetermined internal recess of the crown so that the internal recess of the crown will match the prepared tooth for permanently securing the crown during a single office visit.
It is yet another object of the present invention to control the preparation of a tooth for receipt of a crown so that the external dimensions of the prepared tooth coincide with the internal dimensions of the crown and the exterior surface of the crown matches the original shape of the tooth prior to preparation, including taking an impression of the tooth, preparing the crown and installing the crown during a single office visit.
These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.